feat: console messages API, a reworked logger and browser output kept after startup

[route]

Gives console messages their own API, so nobody has to parse the :logger output to get them (rubycdp/cuprite#113). The logger becomes debug output for Ferrum itself, and Ferrum keeps reading what Chrome writes after startup.

Three feature commits, each can be reviewed on its own, plus two small spec cleanups: an unused helper removed, and the local_browser tag renamed to :launch.

Console

page.console.select(&:error?)
page.console.select { |m| m.match?(/deprecated/) }
page.console.clear
page.on(:console) { |m| logger.public_send(m.severity, m.to_s) }
browser.console # current page
worker.console

• Ferrum::Console is Enumerable over the last 1000 Console::Messages, built from Runtime.consoleAPICalled, Log.entryAdded and Runtime.exceptionThrown. It skips messages Chrome replays from destroyed contexts and log entries from workers.
• Console::Message has type, source, text, args, location, stack_trace, timestamp, severity, error?, warning?, match? and to_s. Text, arguments and stack traces are converted from CDP only when read.
• Breaking: the logger no longer prints [log] ... lines. page.on(:console) { |m| puts m } prints the same text.

Browser output

• Chrome's stdout and stderr used to be read only until the WebSocket URL appeared, and everything after that was lost. A thread now drains the pipe for as long as Chrome runs, and browser.process.output.lines holds the last 100 lines. Process::Output owns the pipe.
• The write end is closed right after spawn, so a Chrome that exits during startup raises ProcessTimeoutError immediately instead of after :process_timeout.

Logging

:logger gets two channels: protocol (CDP messages) and browser (Chrome's output). It can be an IO or a Logger; a Logger gets every line at debug level, with ferrum:protocol or ferrum:browser as program name, and nothing is built when its level is higher.

Env	Values	What it controls
FERRUM_LOG	*, protocol, browser, -browser, Page.*, -Network.*, 0	What gets logged; prints to $stdout when there's no :logger
FERRUM_LOG_FORMAT	default, json, annotated	What CDP lines look like
FERRUM_LOG_VALUE_LENGTH	1024; 0 keeps values whole	Maximum length of a string value in a CDP message
FERRUM_LOG_COLOR	auto, always, never	Color; auto means only on a terminal without NO_COLOR
FERRUM_DEBUG	any value	Deprecated, works as FERRUM_LOG=* and warns once

• FERRUM_LOG: items with a dot are CDP method patterns, and a leading - excludes. Exclusions win, and a response is kept or dropped together with its command.
• Formats:
  • default looks the way the log always has.
  • json writes one message per line as plain JSON, for jq.
  • annotated looks like this:

    ▶ 1.623 #23 Page.navigate {"url":"http://127.0.0.1:5000/console_log"} @4E470240
        ◀ 1.637 #23 Page.navigate 14ms {"frameId":"325D8B09…","loaderId":"64738D2F…"} @4E470240
    

• Long values: they're cut anywhere in a message, not just screenshots, and the JSON stays valid. This replaces FERRUM_LOGGING_SCREENSHOTS, and without a logger, CDP responses are no longer regex-scanned for screenshots.
• Colors: written to a terminal, lines are colored with the basic ANSI colors, which work on light and dark themes.
• Logging never breaks the browser: if formatting or writing a line fails, e.g. a closed IO, Ferrum warns once and skips the line. Messages nested deeper than JSON's default limit of 100 levels, such as large DOM trees, are logged fine.

[Nakilon]

Oh so that's where the "parsing the log" idea came from, lol, that my coworker copied back in the day.
Deepseek then showed how to capture console prior logging just like this:

    page.driver.browser.on("Runtime.exceptionThrown") do |params|
      p params["exceptionDetails"]["exception"]["description"]
    end
    page.driver.browser.on("Runtime.consoleAPICalled") do |params|
      next if [] == values = params["args"].map{ |_| _["value"] }.reject do |v|
        [
          # any exclusion you wanna have
        ].any?{ |r| r === v }
      end
      p values
    end
    page.driver.browser.on("Log.entryAdded") do |params|
      next if [
        # other exclusions
      ].any?{ |r| r === params["entry"]["text"] }
      p params["entry"]["text"]
    end